Here's how to test a good watercolor.   When you look at it from behind, with a strong light in the front, you should see the same picture.   If it has blotches visible it was not painted correctly.   Perhaps an area was laid over with two different colors, the second one being opaque and of a different hue.  Or an erasure mark will show up, or a pencil line.  You can really be proud when it looks the same.